Presently, many types of vacuum motors and by-pass vacuum motors are known. The best example of such a motor, for purposes of appreciating the instant invention, is set forth in U.S. Pat. No. 4,226,575, assigned to the assignee of the invention disclosed herein. In previously known motors of this type, and of motors in general, it is desirable to ground the armature. In previously known motors, such grounding has been a rather simple task, since the end bell or top end bracket receiving the rotating member has been of a metallic nature. Grounding of the top end bracket has achieved the desired armature grounding. However, the advent of high strength plastics, particularly when used for manufacture of the end bell, has eliminated such a grounding technique. Plastic motor housings have necessitated the use of expensive and complex grounding mechanisms.
The motor brushes of the vacuum motors of interest have typically been received in a brush holder which, of necessity, requires time consuming and often complex structures to fixedly secure the brush holder to the motor housing. This significantly increases both the cost and complexity of the motor. Prior to the invention disclosed herein, there has been no inexpensive and simplistic method for securing brushes to the motor housing while assuring that the brush holder is, indeed, secured.
It is known that power wires entering or leaving a motor housing must be secured to prevent inadvertent dislodgment. Typically, a clip, clamp, or the like has been used to secure the wires at the point of entry or exit of the motor housing. Such techniques have required undesirable manufacturing steps and increased the number of parts necessary for the manfacture of the motor, increasing both the cost and complexity of the unit. No method has previously been known by which securement of the power wires is automatically achieved upon assembly of the elements of the motor housing itself.
Further, operational noise levels of vacuum motors have become an increasingly bothersome matter. Each airstream or moving member contributes to the total noise generated by the operating system. In by-pass vacuum motors, where two or more airstreams each contribute noise components to the aggregate noise level, the noise levels may readily become undesirable. Each fan, particularly those in proximity to small orifices or abrupt surfaces tend to contribute significantly to this problem. Accordingly, it is most desirable to achieve a by-pass vacuum motor in which the noise components of the various airstreams are reduced. Particularly, it is desired to reduce the noise component of the motor cooling fan itself.